Virtual image display device and optical unit

Abstract

The invention provides a virtual image display device and an optical unit. The size of an optical system is reduced. A virtual image display device is provided with: a first display panel that emits first image light; a second display panel that emits second image light having a different wavelength band; a third display panel that emits third video light having a different wavelength band; a cross-shaped dichroic prism which has a first light incident surface for the first image light, a second light incident surface for the second image light, and a third light incident surface for the third image light, and which synthesizes the first to third image light; a projection optical system including an optical path bending prism having a first transmissive surface on which the image light from the cross dichroic prism is incident, a first reflective surface for reflecting the image light, a second reflective surface for re-reflecting the image light, and a second transmissive surface from which the image light reflected by the second reflective surface is emitted; and a light guide optical system that is a light guide member that guides the image light emitted from the projection optical system to a pupil position.

Description

Technical Field

[0001] The present invention relates to a virtual image display device and an optical unit capable of observing a virtual image. Background Art

[0002] As a display device capable of observing a virtual image, there is known a display device in which display lights emitted from three display panels are synthesized by a synthesis optical system having two crossed dichroic mirrors so as to be incident from one end of a plate-shaped light guide and emitted from the other end (Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-205451

[0004] In the display device disclosed in Patent Document 1, since a prism-shaped synthetic optical system is used, the size of the optical system up to the light guide portion is likely to be large, and the light guide portion is also large, which results in increased weight, design constraints, etc., which are undesirable results for users. In particular, when the light guide portion is a diffraction type, it is not easy to arrange the synthetic optical system so that it is not perpendicular to the light guide plate constituting the light guide portion but is inclined to the outside or the ear side, and the arrangement and size of the light guide plate are subject to greater constraints. Summary of the invention

[0005] A virtual image display device or an optical unit according to one aspect of the present invention comprises: a first display panel that emits a first image light; a second display panel that emits a second image light having a wavelength band different from that of the first image light; a third display panel that emits a third image light having a wavelength band different from that of the first image light and the second image light; and a cross dichroic prism having a first light incident surface for incident on the first image light, a second light incident surface for incident on the second image light, and a third light incident surface for incident on the third image light, wherein the first image light, the second image light, and the third image light are incident on the third image light. The image light and the third image light are synthesized, and the synthesized image light is emitted from the light emission surface; a projection optical system, which includes a light path bending prism, the light path bending prism having a first transmission surface for the image light from the cross dichroic prism to be incident, a first reflection surface and a second reflection surface for reflecting the image light passing through the first transmission surface, and a second transmission surface for emitting the image light reflected by the second reflection surface; and a light guide component, which guides the image light emitted from the projection optical system to a pupil position where an eye is arranged. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a plan view for explaining a wearing state of the HMD as the first embodiment.

[0007] Figure 2 It is a side view for explaining the arrangement of the optical system constituting the virtual image display device.

[0008] Figure 3 It is a plan view for explaining the arrangement of the optical system constituting the virtual image display device.

[0009] Figure 4 It is a rear view illustrating a light guiding optical system or a light guiding component.

[0010] Figure 5 It is a side view and a rear view explaining the optical system of the first display driving unit.

[0011] Figure 6 This is a stereoscopic image of the appearance of the optical bending prism.

[0012] Figure 7 It is a top view illustrating a virtual image display device according to a modified example.

[0013] Figure 8 It is a side view and a rear view explaining the optical system in the second embodiment.

[0014] Fig. 9 It is a side view and a rear view explaining the optical system in the third embodiment.

[0015] Fig.10 Yes Description Fig. 9 A perspective view of the optical block is shown.

[0016] Fig.11 It is a side view of an optical system for explaining a modified example.

[0017] Description of symbols

[0018] 10: image light generating device; 11: image light emitting unit; 11r, 11b, 11g: display panel; 18: cross dichroic prism; 18ia, 18ib, 18ic: light incident surface; 18o: light emitting surface; 18r, 18b: dichroic mirror; 20: projection optical system; 21, 221, 321: light path bending prism; 22c: inclined plane; 23: lens group; 23a, 23b, 23c: lens; 25: aperture stop; 50: light guide component; 51a: light guide plate; 51b: incident diffraction layer; 51c: emitting diffraction layer; 51e : Pupil enlargement grating layer; 71: retaining member; 88: driving circuit component; 90: user terminal; 100: optical unit; 100A, 100B: virtual image display device; 100C: supporting device; 102a, 102b: display driving unit; 103a, 103b: light guiding optical system; AX: optical axis; CX: cross axis; ML, MLg, MLr, MLb: image light; OX: emission optical axis; PP: pupil position; S1: first transmission surface; S2: first reflection surface; S3: second reflection surface; S4: second transmission surface; US: wearer. DETAILED DESCRIPTION

[0019] First Embodiment

[0020] Below, refer to Figure 1 to Figure 3 etc., a first embodiment of the virtual image display device of the present invention is described.

[0021] Figure 1 1 is a diagram for explaining a wearing state of a head mounted display device (hereinafter also referred to as a head mounted display or HMD) 200, and the HMD 200 allows an observer or wearer US wearing the HMD 200 to recognize a video image as a virtual image. Figure 1 In the above, X, Y, and Z are orthogonal coordinate systems, the +X direction corresponds to the lateral direction in which the two eyes EY of the observer or wearer US wearing the HMD 200 are arranged, the +Y direction corresponds to the upward direction orthogonal to the lateral direction in which the two eyes EY of the wearer US are arranged, and the +Z direction corresponds to the front direction or the front direction of the wearer US. The ±Y directions are parallel to the vertical axis or the vertical direction. In addition, the +Y direction or the upward direction corresponds to the direction from the chin to the center of the forehead of the face when the HMD 200 is worn on the wearer US.

[0022] The HMD 200 includes a first virtual image display device 100A for the right eye, a second virtual image display device 100B for the left eye, a pair of support devices 100C in the shape of temples that support the virtual image display devices 100A and 100B, and a user terminal 90 as an information terminal. The first virtual image display device 100A functions as an HMD alone, and is composed of a first display drive unit 102a arranged at the top and a first light guide optical system 103a that covers the front of the eyes in the shape of a glasses lens. The second virtual image display device 100B also functions as an HMD alone, and is composed of a second display drive unit 102b arranged at the top and a second light guide optical system 103b that covers the front of the eyes in the shape of a glasses lens. The support device 100C is a wearing component worn on the head of the wearer US, and supports the upper end sides of the pair of light guide optical systems 103a and 103b via the display drive units 102a and 102b that are integrated in appearance. The first virtual image display device 100A and the second virtual image display device 100B are optically reversed left and right, and detailed description of the second virtual image display device 100B is omitted.

[0023] Figure 2 1 is a side view specifically illustrating the first display drive unit 102a and the first light guide optical system 103a of the first virtual image display device 100A. Figure 3 1 is a top view specifically illustrating the first display drive unit 102a and the first light guide optical system 103a. Figure 4 It is a rear view mainly explaining the first light guiding optical system 103a.

[0024] Reference Figure 2 as well as Figure 3 The first display driving unit 102a includes an image light generating device 10, a projection optical system 20, and a driving circuit component 88. The image light generating device 10 is an optical engine including an orthogonal prism type image light emitting unit 11. The projection optical system 20 is a collimator including an optical path bending prism 21. The image light ML generated by the image light generating device 10 is collimated by the projection optical system 20 and coupled to the first light guiding optical system 103a as the light guiding component 50. In addition, in the first virtual image display device 100A, the optical device other than the driving circuit component 88 is referred to as an optical unit 100. The image unit 30 formed by combining the image light generating device 10 and the projection optical system 20 is arranged at a position closer to the inside of the eye EY of the wearer US than the first light guiding optical system 103a. The image unit 30 is arranged at the upper part and the outer corner of the eye side in the first light guiding optical system 103a. Here, the upper part of the first light-guiding optical system 103a refers to the upper side of the quadrilateral (edge ​​in the +Y direction), and the outer corner of the first light-guiding optical system 103a refers to the lateral outer side of the quadrilateral (edge ​​in the +X direction). As a result, the image unit 30 is arranged at a position close to the connection portion between the support device 100C and the first virtual image display device 100A.

[0025] Reference Figure 4 The first light guide optical system 103a is a diffraction light guide component capable of performing a color display of RGB three colors, and extends approximately parallel to the XY plane. The first light guide optical system 103a has a light guide plate 51a, an incident diffraction layer 51b, a pupil enlarging grating layer 51e, and an emission diffraction layer 51c. The incident diffraction layer 51b guides the collimated image light ML from the first display drive unit 102a into the light guide plate 51a and propagates it laterally, the pupil enlarging grating layer 51e enlarges the pupil size of the image light ML propagating laterally in the light guide plate 51a and propagates it downward, and the emission diffraction layer 51c enlarges the pupil size of the image light ML propagating downward in the light guide plate 51a and directs the image light ML toward a direction set at the eye EY (refer to Figure 2 ) exists inside the pupil position PP (refer to Figure 2 ) is ejected.

[0026] Figure 5 1 is a diagram for explaining the optical system of the first display drive unit 102a. Figure 5In the figure, area AR1 is a side view of the optical system constituting the first display drive unit 102a, and area AR2 is a rear view of the optical system constituting the first display drive unit 102a. In the first display drive unit 102a, the image light emitting unit 11 includes three display panels 11r, 11b, 11g and a cross-dichroic prism 18. The projection optical system 20 includes a light path bending prism 21 having a positive refractive power and an aperture stop 25. The image light emitting unit 11 and the light path bending prism 21, which are formed by integrating the display panels 11r, 11b, 11g and the cross-dichroic prism 18, are placed on a holder 71 (see FIG. 1 ) which also serves as a cover. Figure 2 ) are supported in a mutually positioned state and fixed to the inner side, i.e., -Z side, of the first light guiding optical system 103a. In addition, the light path bending prism 21 and the light emitting unit 11 are arranged in a vertical arrangement, and the light path bending prism 21 is arranged above the image light emitting unit 11 and the cross dichroic prism 18 assembled therein.

[0027] The display panel 11r for red is the first display panel, and emits red image light MLr as the first image light. The display panel 11r is, for example, an organic EL (Organic Electro-Luminescence) display, which forms a still image or a dynamic image on a two-dimensional display surface parallel to the XY plane, and emits red image light MLr. The display panel 11r for red includes a light-emitting element 14a and a transmissive cover 14b. The light-emitting element 14a is formed by arranging a plurality of image elements two-dimensionally along the XY plane on a substrate. Although not shown in the figure, each image element has the same structure as a general organic EL element, and includes a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and a transparent electrode layer in order from the substrate side.

[0028] The display panel 11b for blue is the second display panel, and emits blue image light MLb as the second image light. The display panel 11b is an organic EL display similar to the display panel 11r for red, and forms a still image or a dynamic image on a two-dimensional display surface parallel to the XY plane, and emits blue image light MLb. The display panel 11b for blue includes a light-emitting element 14a and a transmissive cover 14b. In the display panel 11b for blue, the light-emitting element 14a is formed by arranging a plurality of image elements two-dimensionally along the XY plane. The light-emitting element 14a assembled in the display panel 11b for blue has the same structure as the light-emitting element 14a assembled in the display panel 11r for red, but the light-emitting wavelength is different from that of the light-emitting element 14a of the display panel 11r for red.

[0029] The green display panel 11g is the third display panel, and emits green image light MLg as the third image light. The display panel 11g is an organic EL display similar to the red display panel 11r, and forms a still image or a dynamic image on a two-dimensional display surface parallel to the XZ plane, and emits green image light MLg. The green display panel 11g includes a light-emitting element 14a and a transmissive cover 14b. In the green display panel 11g, the light-emitting element 14a is formed by arranging a plurality of image elements two-dimensionally along the XZ plane. The light-emitting element 14a assembled in the green display panel 11g has the same structure as the light-emitting element 14a assembled in the red display panel 11r, but the light-emitting wavelength is different from that of the light-emitting element 14a in the red display panel 11r.

[0030] It is assumed that the radiation angles of the red image light MLr, the blue image light MLb, and the green image light MLg from the pixel are within about 20°, and the dichroic mirrors 18r and 18b of the cross dichroic prism 18 described later are designed based on this premise, but the present invention is not limited to this.

[0031] The transmissive cover 14b of the display panel 11r for red is fixed in a manner adhered to the first light incident surface 18ib of the cross dichroic prism 18. The first display panel 11r for red causes the red image light MLr as the first image light to enter the cross dichroic prism 18 from the first light incident surface 18ib. The transmissive cover 14b of the display panel 11b for blue is fixed in a manner adhered to the second light incident surface 18ic of the cross dichroic prism 18. The second display panel 11b for blue causes the blue image light MLb as the second image light to enter the cross dichroic prism 18 from the second light incident surface 18ic. The transmissive cover 14b of the display panel 11g for green is fixed in a manner adhered to the third light incident surface 18ia of the cross dichroic prism 18. The third display panel 11g for green causes the green image light MLg as the third image light to enter the cross dichroic prism 18 from the third light incident surface 18ia.

[0032] The cross dichroic prism 18 is a quadrangular prism-shaped component, and has three light incident surfaces 18ia, 18ib, and 18ic as the side surfaces of the quadrangular prism and one light exit surface 18o. The first light incident surface 18ib and the second light incident surface 18ic, which are opposed to each other, extend in parallel, and the third light incident surface 18ia and the light exit surface 18o extend in parallel to each other. The two opposed first light incident surfaces 18ib and the second light incident surface 18ic extend perpendicularly to the third light incident surface 18ia disposed therebetween.

[0033] The cross dichroic prism 18 is formed by joining four right-angled triangular prisms 18a formed of glass materials or the like in a manner that the right-angled edges are consistent, and has a structure in which two orthogonal dichroic mirrors 18r and 18b are embedded in the boundaries or joints of the four right-angled triangular prisms 18a. One dichroic mirror 18r extends perpendicularly to a reference direction D1, which is parallel to the YZ plane and is 45° relative to the Y direction and the -Z direction. That is, the dichroic mirror 18r is configured to form an angle of 45° with the first incident surface 18ib. The dichroic mirror 18r forms a surface connecting the diagonals of the square outline when observed from the direction of the cross axis CX of the cross dichroic prism 18. The other dichroic mirror 18b extends perpendicularly to a reference direction D2 perpendicular to the reference direction D1, based on a reference direction D1 that is parallel to the YZ plane and is 45° relative to the Y direction and the -Z direction. That is, the dichroic mirror 18b is disposed to form an angle of 45° with the second incident surface 18ic. The dichroic mirror 18b forms a surface connecting diagonal corners of a square outline when viewed from the direction of the cross axis CX of the cross dichroic prism 18.

[0034] The red image light MLr incident on the first incident surface 18ib of the cross dichroic prism 18 from the first display panel 11r for red is reflected by the dichroic mirror 18r and bent toward the emission side, that is, the optical axis AX side, and emitted from the light emission surface 18o to the external +Y direction. The blue image light MLb incident on the second incident surface 18ic of the cross dichroic prism 18 from the second display panel 11b for blue is reflected by the dichroic mirror 18b and bent toward the emission side, that is, the optical axis AX side, and emitted from the light emission surface 18o to the external +Y direction. The green image light MLg incident on the third incident surface 18ia of the cross dichroic prism 18 from the third display panel 11g for green is not reflected by the dichroic mirrors 18r and 18b, but passes toward the optical axis AX side, and is emitted from the light emission surface 18o to the external +Y direction. That is, the cross dichroic prism 18 allows the green image light MLg to pass through. As a result, the cross dichroic prism 18 can synthesize an image in which the red image light MLr, the green image light MLg, and the blue image light MLb are superimposed, and the image is emitted as the image light ML and enters the projection optical system 20 .

[0035] In the cross dichroic prism 18, the cross axis CX extends along the intersection of the two dichroic mirrors 18r and 18b, and is parallel to the X direction. The first optical axis X1 extending from the center of the first display panel 11r for red to the cross axis CX of the cross dichroic prism 18 is parallel to the Z direction. The second optical axis X2 extending from the center of the display panel 11b for blue to the cross axis CX of the cross dichroic prism 18 is parallel to the Z direction. The third optical axis X3 extending from the center of the display panel 11g for green to the cross axis CX of the cross dichroic prism 18 is parallel to the Y direction. The optical axis AX extending from the center of the cross axis CX to the light exit surface 18o of the cross dichroic prism 18 extends in parallel to the Y direction on the extension line of the third optical axis X3.

[0036] As described above, the optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the longitudinal direction parallel to the light guide plate 51a, that is, in the Y direction. As a result, the projection optical system 20 including the light path bending prism 21 and the cross dichroic prism 18 can be arranged along the light guide plate 51a, and the height of the optical system protruding from the light guide plate 51a can be reduced. In addition, the cross axis CX of the cross dichroic prism 18 extends parallel to the light guide plate 51a. In this case, the display panels 11r, 11b, and 11g have an aspect ratio of being horizontally long, and the size in the X direction parallel to the cross axis CX is relatively large. Therefore, the cross-sectional size of the cross dichroic prism 18 observed from the X direction can be reduced, and the cross dichroic prism 18 can be easily brought close to the light guide plate 51a.

[0037] The light path bending prism 21 of the projection optical system 20 is an optical component having a refraction and reflection function, and has a function of combining a reflector and a lens, and refracts and reflects the image light ML emitted from the cross dichroic prism 18 of the image light emitting unit 11. The light path bending prism 21 has a first transmission surface S1 as a convex refractive surface, a first reflection surface S2 as a concave reflection surface, a second reflection surface S3 as a concave reflection surface, and a second transmission surface S4 as a flat refractive surface as optical surfaces. An aperture stop 25 is provided on the second transmission surface S4.

[0038] Figure 6 : is a perspective view of the appearance of the optical path bending prism 21. The optical path bending prism 21 has a pentagonal prism shape that is long in the X direction. In the optical path bending prism 21, the inclined surface 22c connecting the first reflecting surface S2 and the second reflecting surface S3 is a connecting surface CS that does not perform an optical function, and can be a flat surface or a curved surface. The optical path bending prism 21 has a pair of side surfaces 22d at both ends in the horizontal direction. The optical path bending prism 21 has a relatively long horizontal profile corresponding to the aspect ratio of the display panels 11r, 11b, and 11g.

[0039] return Figure 5The optical path bending prism 21 makes the image light ML incident from the bottom where the image light emitting unit 11 is arranged bend forward and emit it. The first transmission surface S1, the first reflection surface S2 and the second reflection surface S3 constituting the optical path bending prism 21 have positive refractive power. The first transmission surface S1, the first reflection surface S2 and the second reflection surface S3 are asymmetric about the optical axis AX in the longitudinal direction parallel to the YZ plane and intersecting the optical axis AX, and are symmetric about the optical axis AX in the transverse direction or the X direction. The first transmission surface S1, the first reflection surface S2 and the second reflection surface S3 are, for example, free-form surfaces. The first transmission surface S1, the first reflection surface S2 and the second reflection surface S3 are not limited to free-form surfaces, and can also be aspherical surfaces. The optical path bending prism 21 is made of glass or resin. The first reflecting surface S2 and the second reflecting surface S3 as reflecting surfaces can be set to reflect the image light ML by total reflection, but can also be set as a reflecting surface composed of a metal film or a dielectric multilayer film. In this case, a reflecting film composed of a single layer film or a multilayer film composed of a metal such as Al or Ag is formed on the first reflecting surface S2 and the second reflecting surface S3 by evaporation or the like. Although detailed illustration is omitted, an anti-reflection film can be formed on the first transmission surface S1 and the second transmission surface S4.

[0040] The reflecting surfaces S2 and S3 may be structural reflecting surfaces such as wire grids, or reflective polarizing films. As structural reflecting surfaces, for example, a wire grid polarizer having a fine wire grid structure made of aluminum formed on a resin film substrate may be used. A reflective polarizing film is a polarization separation film having a multilayer structure formed on a resin film substrate. That is, the reflecting surface of the optical path bending prism 21 may be a structure having a plurality of metal films or dielectrics stacked on top of each other, or a structure having a fine structure on the surface.

[0041] The optical axis AX of the second transmission surface S4 passing through the optical path bending prism 21 is the optical axis on the emission side of the projection optical system 20, and extends perpendicularly to the light guide plate 51a. Furthermore, the optical axis AX of the first transmission surface S1 passing through the optical path bending prism 21 and the optical axis AX of the second transmission surface S4 passing through the optical path bending prism 21 are perpendicular and orthogonal to each other. In this case, the optical path is bent 90° before and after passing through the optical path bending prism 21, and the cross dichroic prism 18 can be arranged along the light guide plate 51a. By adjusting the angular relationship between the first reflection surface S2, the second reflection surface S3, etc., the optical axis AX of the incident side of the first transmission surface S1 passing through the optical path bending prism 21 and the optical axis AX of the emission side passing through the second transmission surface S4 can be made into a state other than being orthogonal. When the angle φ between the optical axis AX passing through the first transmission surface S1 and the optical axis AX passing through the second transmission surface S4 is, for example, an obtuse angle, the cross dichroic prism 18 is arranged at a position that is offset in the -Z direction and relatively far from the light guide plate 51a from the optical path bending prism 21, and the distance from the light guide plate 51a can be adjusted. In this way, the optical path bending prism 21 not only bends the optical path to substantially shorten it, but also functions like a joint with respect to the optical path, so that the degree of freedom of arrangement of the cross dichroic prism 18 can be increased.

[0042] In the optical path bending prism 21, the angle formed by the optical axis AX before and after reflection by the first reflecting surface S2 is α, and the angle formed by the optical axis AX before and after reflection by the second reflecting surface S3 is β. The angle α and the angle β are substantially equal to prevent excessive off-axis and difficulty in aberration correction. In addition, the reference axis RX2 of the first reflecting surface S2 corresponding to the bisector of the optical axis AX before and after reflection by the first reflecting surface S2 and the reference axis RX3 of the second reflecting surface S3 corresponding to the bisector of the optical axis AX before and after reflection by the second reflecting surface S3 form an obtuse angle γ with the inward direction as a reference. This means that the first reflecting surface S2 and the second reflecting surface S3 are generally arranged to be opposite to each other at an acute angle compared to the vertical, and the optical axis AX incident on the first reflecting surface S2 and the optical axis AX emitted from the second reflecting surface S3 can intersect.

[0043] The optical path bending prism 21 is an optical system that is substantially telecentric with respect to the image light emitting unit 11, which is the object side. That is, the principal rays of the image lights MLg, MLr, and MLb emitted from the respective portions of the display surfaces of the display panels 11b, 11r, and 11g pass through the cross dichroic prism 18 via the light incident surfaces 18ib, 18ic, and 18ia in a state substantially parallel to the optical axes X1, X2, and X3, and are emitted from the cross dichroic prism 18 substantially parallel to the optical axis AX. Thus, the red image light MLr, the green image light MLg, and the blue image light MLb that are less than a predetermined angle range are incident on the dichroic mirrors 18r and 18b, and the light loss caused by the dichroic mirrors 18r and 18b can be suppressed.

[0044] The optical path bending prism 21 makes the image lights MLg, MLr, and MLb emitted from the display surfaces of the display panels 11b, 11r, and 11g enter the central area of ​​the incident diffraction layer 51b of the light guide plate 51a while being collimated. At this time, the image lights MLg, MLr, and MLb pass through the opening 25a of the aperture stop 25. The aperture stop 25 suppresses the generation of stray light.

[0045] return Figure 4 In the first light guide optical system 103a or the light guide component 50, the incident diffraction layer 51b is the first diffraction element, which is formed by a diffraction pattern that extends linearly in the longitudinal Y direction and is periodically repeated in the transverse X direction. The emission diffraction layer 51c is the second diffraction element, which is formed by a diffraction pattern that extends linearly in the transverse X direction and is periodically repeated in the longitudinal Y direction. The pupil enlargement grating layer 51e is the third diffraction element, which is arranged on the +X side of the incident diffraction layer 51b, and bends the optical path of the image light ML guided into the light guide plate 51a and traveling in the +X direction as a whole to travel in the -Y direction as a whole.

[0046] The incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil magnification grating layer 51e diffract according to the wavelength of the image light MLg, MLr, and MLb, and are formed, for example, by a surface relief type diffraction element. The surface relief type diffraction element is formed by nanoimprinting, but is not limited thereto, and can also be formed by etching the surface of the light guide plate 51a, or by pasting a diffraction element. The incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil magnification grating layer 51e can also be formed by a volume hologram. The incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil magnification grating layer 51e are not limited to being composed of a single layer, and can also be stacked with multiple functional layers suitable for the wavelength of the image light ML and the direction of the field of view angle. The light guide plate 51a is formed of plastic or glass. When formed of plastic, the thickness can be set to, for example, about 1 mm, and when formed of glass, the thickness can be set to, for example, about 0.3 mm to 0.4 mm.

[0047] The pupil enlargement grating layer 51e changes the diffraction direction without substantially damaging the angle information of the image light ML related to the left and right X direction and the angle information of the image light ML related to the up and down Y direction. The pupil enlargement grating layer 51e is interposed between the incident diffraction layer 51b and the emission diffraction layer 51c, and guides the image light ML in a direction (-Y direction) intersecting the diffraction direction (-X direction) of the incident diffraction layer 51b and splits the light, and has the function of enlarging the lateral width of the light. The pupil enlargement grating layer 51e is formed by a diffraction pattern that extends linearly in the DS2 direction parallel to and inclined to the XY plane and is periodically repeated in the DS1 direction parallel to the XY plane and perpendicular to the DS2 direction. The DS1 direction is a direction rotated 45° clockwise relative to the +Y direction, and is an intermediate direction between the -X direction and the +Y direction. The grating period or pitch in the X and Y directions of the pattern formed in the pupil enlargement grating layer 51e is consistent with the grating period in the X direction of the pattern formed in the incident diffraction layer 51b, and is consistent with the grating period in the Y direction of the pattern formed in the emission diffraction layer 51c. The emission diffraction layer 51c guides the image light ML in the -Y direction and splits the light, which has the effect of expanding the longitudinal light width. As a result, the incident light ML Figure 2 The image light ML at the pupil position PP shown in FIG. 1 has a light width in the X and Y directions that is extended corresponding to the emission diffraction layer 51c. The pupil size increases in the longitudinal and lateral directions after passing through the pupil enlargement grating layer 51e, the emission diffraction layer 51c, etc. The light is emitted from the emission diffraction layer 51c with an emission optical axis OX (refer to FIG. 1 ) perpendicular to the light guide plate 51a. Figure 2 ) is the collimated image light ML centered at the emitting diffraction layer 51c. The image light ML emitted from the emitting diffraction layer 51c is within a range of about ±25° with respect to the emitting optical axis OX. That is, the viewing angle of the first virtual image display device 100A is about 50°.

[0048] In the above description, the optical axis AX passing through the light exit surface 18o of the cross dichroic prism 18 extends in the longitudinal direction Y, but the optical axis AX passing through the light exit surface 18o may also extend in the transverse direction X. In this case, the optical path bending prism 21 and the cross dichroic prism 18 are arranged in the transverse direction X along the light guide plate 51a.

[0049] In the above description, the optical axis AX passing through the second transmission surface S4 of the optical path bending prism 21 extends perpendicularly to the light guide plate 51a, but the optical axis AX emitted from the optical path bending prism 21 can be tilted from the state perpendicular to the light guide plate 51a. Figure 6 The angular relationship between the second reflecting surface S3 and the second transmitting surface S4 of the optical path bending prism 21 shown in the figure can be adjusted so that the direction of the optical axis AX emitted from the second transmitting surface S4 is inclined to the desired direction and angle relative to the normal direction thereof.

[0050] The display panels 11 b , 11 r , and 11 g are not limited to organic EL, and can be replaced by display devices using LED arrays, laser arrays, quantum dot light-emitting elements, and the like.

[0051] A polarizing plate or a filter may be interposed between the transmissive cover 14 b of the display panels 11 b , 11 r , and 11 g and the light incident surfaces 18 ib , 18 ic , and 18 ia of the cross dichroic prism 18 .

[0052] The light guide plate 51a or the incident diffraction layer 51b and the second transmission surface S4 of the optical path bending prism 21 do not need to be separated, and they can be brought into close contact.

[0053] exist Figure 7 In the modified example shown, by adjusting the shape of the optical path bending prism 21, the optical axis AX emitted from the projection optical system 20 is tilted toward the nose side or the -X side on the projection optical system 20 side or the upstream side, based on the state perpendicular to the light guide plate 51a. As a result, the emission optical axis OX can be tilted toward the ear side or the +X side on the pupil side, the light guide plate 51a can be tilted by rotating counterclockwise based on the longitudinal Y axis, and the configuration of the light guide plate 51a can be made to fit the face. As shown in the figure, in order to tilt the optical axis AX emitted from the projection optical system 20 when viewed from the Y axis direction or the upward direction, the optical unit 100 or the image unit 30 is rotated integrally around an axis parallel to the Y axis.

[0054] The virtual image display device 100A, 100B of the first embodiment comprises: a first display panel 11r, which emits red image light MLr as the first image light; a second display panel 11b, which emits blue image light MLb as the second image light having a wavelength band different from that of the first image light; a third display panel 11g, which emits green image light MLg as the third image light having a wavelength band different from that of the first image light and the second image light; a cross-dichroic prism 18, which comprises a first light incident surface 18ib for incidenting the first image light, i.e., the red image light MLr, a second light incident surface 18ic for incidenting the second image light, i.e., the blue image light MLb, and a third light incident surface 18ia for incidenting the third image light, i.e., the green image light MLg, The projection optical system 20 comprises a light path bending prism 21, wherein the light path bending prism 21 has a first transmission surface S1 for incident image light ML from the cross dichroic prism 18, a first reflection surface S2 for reflecting image light ML having passed through the first transmission surface S1, a second reflection surface S3 for reflecting image light ML reflected by the first reflection surface S2, and a second transmission surface S4 for emitting image light ML reflected by the second reflection surface S3; and light guide optical systems 103a and 103b as light guide components 50 for guiding image light ML emitted from the projection optical system 20 to a pupil position PP at which an eye is disposed.

[0055] In the above-mentioned virtual image display apparatuses 100A and 100B, the optical path bending prism 21 included in the projection optical system 20 has: a first transmission surface S1, which allows the image light ML from the cross dichroic prism 18 to be incident; a first reflection surface S2, which reflects the image light ML that has passed through the first transmission surface S1; a second reflection surface S3, which reflects the image light ML reflected by the first reflection surface S2; and a second transmission surface S4, which emits the image light ML reflected by the second reflection surface S3. Therefore, the optical path is bent in the optical path bending prism 21, and the optical path can be increased, and the imaging performance can be easily improved. In addition, as a result of being able to make the optical axis AX incident on the optical path bending prism 21 and the optical axis AX emitted from the optical path bending prism 21 have a desired angle difference, the degree of freedom of the configuration of the cross dichroic prism 18 is improved, and the overall optical system can be miniaturized.

[0056] Second Embodiment

[0057] Hereinafter, a virtual image display device according to a second embodiment of the present invention will be described. Note that the virtual image display device according to the second embodiment is obtained by partially changing the virtual image display device according to the first embodiment, and description of the same parts will be omitted.

[0058] Figure 8 FIG. 2 is a diagram for explaining a virtual image display device according to a second embodiment. Figure 8 In FIG. 1 , region BR1 is a side view of the optical system constituting the first display drive unit 102 a , and region BR2 is a rear view of the optical system constituting the first display drive unit 102 a .

[0059] As shown in the figure, in the virtual image display device of the second embodiment, the projection optical system 20 of the first display driving unit 102a has a light path bending prism 221 without refractive power and a lens group 23. The light path bending prism 221 has, as an optical surface, a first transmission surface S1 as a refractive surface of a plane, a first reflection surface S2 as a reflection surface of a plane, a second reflection surface S3 as a reflection surface of a plane, and a second transmission surface S4 as a refractive surface of a plane. In addition, the lens group 23 has positive refractive power as a whole, and has a first lens 23a, a second lens 23b and a third lens 23c. These lenses 23a, 23b, and 23c have positive refractive power respectively. The angle relationship between the surfaces S1, S2, S3, and S4 is not limited to the figure and can be changed. Thus, the direction of the optical axis AX passing through the light emitting surface 18 o of the cross dichroic prism 18 can be freely adjusted relative to the light guide plate 51 a , and the protruding direction of the cross dichroic prism 18 relative to the light guide plate 51 a can be freely adjusted.

[0060] In addition, the number of lenses constituting the lens group 23 is not limited to three, and may be one, two, or four or more.

[0061] Third Embodiment

[0062] Hereinafter, a virtual image display device according to a third embodiment of the present invention will be described. Note that the virtual image display device according to the third embodiment is obtained by partially changing the virtual image display device according to the first embodiment, and description of the same parts will be omitted.

[0063] Fig. 9 FIG. 2 is a diagram for explaining a virtual image display device according to a third embodiment. Fig. 9 In FIG. 1 , region CR1 is a side view of the optical system constituting the first display drive unit 102 a , and region CR2 is a top view of the optical system constituting the first display drive unit 102 a . Fig.10 It is a perspective view of an optical system constituting the first display drive unit 102a.

[0064] As shown in the figure, in the virtual image display device of the third embodiment, the projection optical system 20 of the first display driving unit 102a is composed only of an optical path bending prism 321 having a positive refractive power. The optical path bending prism 321 has a first transmission surface S1 as a flat refractive surface, a first reflection surface S2 as a concave reflection surface, a second reflection surface S3 as a concave reflection surface, and a second transmission surface S4 as a flat refractive surface as optical surfaces. Here, the first reflection surface S2 and the second reflection surface S3 have positive refractive power. The first transmission surface S1 of the optical path bending prism 321 is a flat surface, and is joined to the light emitting surface 18o of the cross dichroic prism 18. That is, the cross dichroic prism 18 and the optical path bending prism 321 are integrated and can be handled as one block. Furthermore, by making the first transmission surface S1 abut against the light emitting surface 18o, the light path bending prism 321 can be positioned relative to the cross dichroic prism 18 regarding rotation around the X axis and rotation around the Z axis, and can be fixed with high precision, thereby easily realizing miniaturization and high precision of the first display driving unit 102a.

[0065] In the case of this embodiment, it is easy to generate image light ML from the cross dichroic prism 18 through the optical path bending prism 321. Therefore, sometimes when the divergence angle component of the image light ML from each pixel is large, it is better to separate the second transmission surface S4 of the optical path bending prism 321 from the light guide plate 51a or the incident diffraction layer 51b.

[0066] Other matters

[0067] The above-described structure is an example, and various changes can be made within the range in which the same function can be achieved.

[0068] The optical path bending prism 21 is not limited to having a first transmission surface S1 for incident image light ML, a first reflection surface S2 for reflecting image light ML that has passed through the first transmission surface S1, a second reflection surface S3 for reflecting image light ML reflected by the first reflection surface S2, and a second transmission surface S4 for emitting image light ML reflected by the second reflection surface S3. A third reflection surface may also be provided for causing image light ML reflected by the first reflection surface S2 to be incident on the second reflection surface S3.

[0069] The aperture stop 25 provided additionally on the second transmission surface S4 which is the emission surface of the optical path bending prism 21 is not essential.

[0070] By slightly shifting the configuration of the display panels 11b, 11r, and 11g in the vertical and horizontal directions, the exit pupil of the light path bending prism 21 can be configured differently for each color. In this case, in the aperture stop 25, a plurality of openings 25a suitable for each color can be staggered in the X direction and the Y direction. At this time, the incident diffraction layer 51b can be set according to the openings 25a of each color or in a manner covering all the openings 25a. The light guide component 50 can also be a component formed by overlapping a plurality of light guide plates or light guide bodies in parallel. For example, consider setting the first light guide plate for RG and the second light guide plate for BG. In this case, in the first light guide plate and the second light guide plate, the region of the incident diffraction layer is set in a manner opposite to the opening 25a for the G color.

[0071] When the angle φ formed by the optical axis AX of the first transmission surface S1 passing through the optical path bending prism 21 and the optical axis AX of the second transmission surface S4 passing through the optical path bending prism 21 is an obtuse angle, the cross-color separation prism 18 tends to protrude more than the optical path bending prism 21 with respect to the light guide plate 51a, but it is easy to ensure space for accommodating the display panels 11b, 11r, 11g and their associated driving circuits.

[0072] The light guide member 50 is not limited to including the incident diffraction layer 51b, the emission diffraction layer 51c, and the pupil enlargement grating layer 51e, and for example, the pupil enlargement grating layer 51e may be omitted. In this case, the incident diffraction layer 51b guides the collimated image light ML into the light guide plate 51a and causes it to propagate in the lateral direction, and the emission diffraction layer 51c causes the image light ML propagating in the lateral direction in the light guide plate 51a to be emitted toward the inner pupil position PP.

[0073] The light guide member 50 may also be a member formed by overlapping a plurality of light guides in parallel. In this case, each light guide as a component can correspond to three colors, RBG, for example. Each light guide includes a light guide plate 51a, an incident diffraction layer 51b, an emission diffraction layer 51c, and a pupil magnifying grating layer 51e.

[0074] like Fig.11 As shown, the light guide member 50 may also be provided with an incident diffraction layer 51b, an outgoing diffraction layer 51c and a pupil magnifying grating layer 51e on the outer side of the light guide plate 51a. In this case, the incident diffraction layer 51b, the outgoing diffraction layer 51c and the pupil magnifying grating layer 51e all become reflective diffraction elements.

[0075] about Figure 8 The optical path bending prism 221 shown can set, among the optical surfaces constituting the prism, for example, the first transmission surface S1 as a convex refractive surface, or can set the first reflection surface S2, the second reflection surface S3, etc. as concave reflection surfaces.

[0076] In the first display driving unit 102a, the optical system formed by combining the cross dichroic prism 18 and the optical path bending prism 21 is not limited to an optical system that couples the image light ML to the first light guide optical system 103a as a diffraction light guide component, but may be an optical system that couples the image light ML to various non-diffraction light guide plates, or an optical system that couples the image light ML to a birdbath type light guide component. As various non-diffraction light guide plates, for example, a region in which a plurality of split reflectors are embedded can be provided in a portion corresponding to a diffraction element in one light guide plate to couple the image light ML.

[0077] As described above, the virtual image display devices 100A and 100B can be used as HMDs, but the present invention is not limited thereto and can be applied to various optical devices. For example, the present invention can also be applied to a head-up display (HUD).

[0078] The virtual image display device in a specific embodiment comprises: a first display panel that emits a first image light; a second display panel that emits a second image light having a wavelength band different from that of the first image light; a third display panel that emits a third image light having a wavelength band different from that of the first image light and the second image light; a cross dichroic prism having a first light incident surface for incident on the first image light, a second light incident surface for incident on the second image light, and a third light incident surface for incident on the third image light, The third image light is synthesized and the synthesized image light is emitted from the light emission surface; a projection optical system, which includes a light path bending prism, the light path bending prism having a first transmission surface for incident image light from the cross dichroic prism, a first reflection surface and a second reflection surface for reflecting image light passing through the first transmission surface, and a second transmission surface for emitting image light reflected by the second reflection surface; and a light guiding component, which guides the image light emitted from the projection optical system to a pupil position where an eye is arranged.

[0079] In the above-mentioned virtual image display device, the light path bending prism included in the projection optical system has a first transmission surface for incident image light from the cross dichroic prism, a first reflection surface and a second reflection surface for reflecting the image light transmitted through the first transmission surface, and a second transmission surface for emitting the image light reflected by the second reflection surface. Therefore, the light path is bent in the light path bending prism, and the light path can be increased, and the imaging performance can be easily improved. In addition, as a result of being able to make the optical axis incident on the light path bending prism and the optical axis emitted from the light path bending prism have a desired angle difference, the degree of freedom of configuration of the cross dichroic prism is improved, and the optical system as a whole can be miniaturized.

[0080] In a specific embodiment of the virtual image display device, the optical path bending prism has a positive refractive power. In this case, the optical path bending prism helps to form a part of the collimator, which makes it easy to reduce the number of optical components constituting the projection optical system.

[0081] In a specific embodiment of the virtual image display device, the first reflecting surface has positive refractive power.

[0082] In a specific embodiment of the virtual image display device, the second reflecting surface has a positive refractive power. In this case, the necessity of incorporating a lens into the projection optical system can be reduced.

[0083] In a specific embodiment of the virtual image display device, the first transmission surface has a positive refractive power. In this case, the necessity of incorporating a lens into the projection optical system can be reduced.

[0084] In a specific embodiment of the virtual image display device, the first transmission surface is a flat surface and is joined to the light emitting surface of the cross dichroic prism. In this case, the cross dichroic prism and the optical path bending prism are easily positioned.

[0085] In a specific embodiment of the virtual image display device, the projection optical system includes a lens arranged between the cross dichroic prism and the light path bending prism.

[0086] In a specific embodiment of the virtual image display device, the optical axis of the first transmission surface passing through the optical path bending prism is perpendicular to or at an obtuse angle to the optical axis of the second transmission surface passing through the optical path bending prism. In this case, the optical path can be appropriately bent before and after passing through the optical path bending prism, and the cross dichroic prism can be easily arranged close to the light guide component.

[0087] In a specific embodiment of the virtual image display device, the light guide member includes: a flat light guide plate; an incident diffraction layer attached to the light guide plate; and an emission diffraction layer attached to the light guide plate and disposed at a position different from the incident diffraction layer. In this case, the light guide member can be used to propagate image light from the incident diffraction layer to the emission diffraction layer while performing pupil dilation.

[0088] In a specific embodiment of the virtual image display device, an optical axis on the emission side of the projection optical system extends perpendicularly to the light guide plate.

[0089] In a specific embodiment of the virtual image display device, the optical axis of the light exiting surface of the cross dichroic prism extends parallel to the light guide plate. In this case, the optical path bending prism and the cross dichroic prism can be arranged along the light guide plate, and the height of the optical system protruding from the light guide plate can be reduced.

[0090] In a specific embodiment of the virtual image display device, the light path bending prism is arranged above the cross dichroic prism.

[0091] In a specific embodiment of the virtual image display device, the cross axis of the cross dichroic prism extends parallel to the light guide plate. In this case, when the aspect ratio of the display panel is large in the direction parallel to the cross axis, the cross dichroic prism is easily brought close to the light guide plate.

[0092] In a specific embodiment of the virtual image display device, an aperture stop is provided in addition to the second transmission surface of the optical path bending prism. In this case, it is easy to suppress the generation of stray light.

[0093] The optical unit in a specific embodiment comprises: a first display panel that emits a first image light; a second display panel that emits a second image light having a wavelength band different from that of the first image light; a third display panel that emits a third image light having a wavelength band different from that of the first image light and the second image light; a cross dichroic prism having a first light incident surface for incident the first image light, a second light incident surface for incident the second image light, and a third light incident surface for incident the third image light, The third image light is synthesized, and the synthesized image light is emitted from the light emission surface; a projection optical system, which includes a light path bending prism, the light path bending prism has a first transmission surface for image light from the cross dichroic prism to be incident, a first reflection surface and a second reflection surface for reflecting the image light passing through the first transmission surface, and a second transmission surface for emitting the image light reflected by the second reflection surface; and a light guide component, which guides the image light emitted from the projection optical system to the pupil position where the eye is arranged.

Claims

1. A virtual image display device, comprising: a first display panel that emits a first image light; a second display panel emitting a second image light having a wavelength band different from that of the first image light; a third display panel emitting a third image light having a wavelength band different from that of the first image light and the second image light; a cross dichroic prism having a first light incident surface for incident on the first image light, a second light incident surface for incident on the second image light, and a third light incident surface for incident on the third image light, synthesizing the first image light, the second image light, and the third image light, and emitting the synthesized image light from a light emitting surface; a projection optical system comprising a light path bending prism, the light path bending prism having a first transmission surface for incident image light from the cross dichroic prism, a first reflection surface and a second reflection surface for reflecting the image light transmitted through the first transmission surface, and a second transmission surface for emitting the image light reflected by the second reflection surface; and A light guide member guides the image light emitted from the projection optical system to a pupil position where an eye is arranged.

2. The virtual image display device according to claim 1, wherein: The optical path bending prism has positive refractive power.

3. The virtual image display device according to claim 2, wherein: The first reflecting surface has positive refractive power.

4. The virtual image display device according to claim 3, wherein: The second reflecting surface has positive refractive power.

5. The virtual image display device according to claim 2, wherein: The first transmission surface has positive refractive power.

6. The virtual image display device according to claim 2, wherein: The first transmission surface is a flat surface and is joined to the light emitting surface of the cross dichroic prism.

7. The virtual image display device according to claim 1, wherein: The projection optical system includes a lens disposed between the cross dichroic prism and the light path bending prism.

8. The virtual image display device according to claim 1, wherein: The optical axis passing through the first transmission surface of the optical path bending prism is perpendicular to or forms an obtuse angle with the optical axis passing through the second transmission surface of the optical path bending prism.

9. The virtual image display device according to claim 1, wherein: The light guide member includes: a flat light guide plate; an incident diffraction layer attached to the light guide plate; and an output diffraction layer attached to the light guide plate and provided at a position different from the incident diffraction layer.

10. The virtual image display device according to claim 9, wherein: An optical axis of the projection optical system on the emission side extends perpendicularly to the light guide plate.

11. The virtual image display device according to claim 10, wherein: An optical axis passing through the light exit surface of the cross dichroic prism extends parallel to the light guide plate.

12. The virtual image display device according to claim 11, wherein: The optical path bending prism is arranged above the cross dichroic prism.

13. The virtual image display device according to claim 11, wherein: A crossing axis of the cross dichroic prism extends parallel to the light guide plate.

14. The virtual image display device according to claim 1, wherein: An aperture stop is attached to the second transmission surface of the optical path bending prism.

15. An optical unit comprising: a first display panel that emits a first image light; a second display panel emitting a second image light having a wavelength band different from that of the first image light; a third display panel emitting a third image light having a wavelength band different from that of the first image light and the second image light; a cross dichroic prism having a first light incident surface for incident on the first image light, a second light incident surface for incident on the second image light, and a third light incident surface for incident on the third image light, synthesizing the first image light, the second image light, and the third image light, and emitting the synthesized image light from a light emitting surface; a projection optical system comprising a light path bending prism, the light path bending prism having a first transmission surface for incident image light from the cross dichroic prism, a first reflection surface and a second reflection surface for reflecting the image light transmitted through the first transmission surface, and a second transmission surface for emitting the image light reflected by the second reflection surface; and A light guide member guides the image light emitted from the projection optical system to a pupil position where an eye is arranged.

Images